Short Version
HB and I madeout twice but had to quit because of time constraints, lack of isolation, and we're trying to keep it a secret. (Definite F-close otherwise.)
We now have a semi-Day 2 with her roommate there (in a public building complex).

Where do I start from?

The best situation I can think of is isolating her in the building somewhere and just F-close her in some room off to the side.

I don't want to become the "makeout guy", because I think we could be FBs.

Long Version
(HB is in another social circle, but our circles meet up A LOT.)

This past weekend, I get to the club and HB immediately puts her arm around me. We banter for a good 5/10min then we mingle with others and then back with her arm around me again. (TONS of kino and energy.)

So, we get to the after-party which is basically us sitting around and bantering with each other. I've got HB on one side of me and HBblondie on the other side, switching between conversations with both of them. (Meanwhile, AFC1 & AFC2 are sitting just watching.)

Eventually, during the convos, HB knows HBblondie is going for the kill, so HB puts her arm around me again. (AFC1 then puts HIS arm around HB and inside my head I'm just dying of laughter because he can't take a fucking clue.)

So, I make another drink in the kitchen and HB follows me and starts making out with me for a good minute. We hear someone and break it up before AFC1 enters.

In a normal situation, I'd have taken HB downstairs in the laundry room and F-close, but my EX was there. (We're still really close friends and she's not over me) and she was giving me the death stare because of all my flirting.

We eventually isolate and start making out hardcore for a good 5 minutes. However, in the back of my mind, I know everyone is going to start wondering where we are. I stop and tell her that we'll continue it later.

Except, there was no "later". Everyone had to go home.

The Day 2 should have plenty of non-sexual kino opportunity.

Should of just F closed at the first opportunity my dude! By the sounds of she's definitely into you and if you play this right you can make her a FB

I suggest when you go out with her and her roomie, relax and honestly just have a good time. You've got it in the bag regardless of what you do. Be funny and even flirt with her roomate a bit(assuming she's cute)

Then whenever you guys are just hanging around by her building/apartment, find an excuse to isolate the 2 of you. Could be as easy as "give me a grande tour of this place" or "show me your bathroom is"

Keep the kino escalation high during the date, touch her any chance you get for literally anything

Play it cool and once you get isolated just the two of you, go in for the kill

Good luck buddy